1. Field of the Invention
The invention relates to a level shifter, and more particularly to a two-stage level shifter with a boost circuit.
2. Brief Description of the Related Art
The conventional voltage pull-up circuit is typically implemented by a level shifter. The level shifter includes two input terminals respectively receiving an input signal and an inverted input signal. In a typical level shifter, the input terminal is electrically connected to the gate of a transistor. If the output current of the level shifter needs to be increased, the W/L ratio of the transistor coupled to the input terminal must be raised firstly, thus, the layout area of the level shifter will be increased. To completely turn on an NMOS transistor, the input positive voltage applied to the gate of the NMOS transistor must exceed a predetermined voltage level. If the input positive voltage applied to the gate of the NMOS transistor does not exceed the predetermined voltage level, the NMOS transistor can not be completely turned on and only outputs small output current. If the voltage level of the input signal applied to the level shift does not exceed a predetermined voltage level, the level shifter may be not properly driven.